PROGRAM SUMMARY In 2013, AIDS was the leading cause of mortality among adolescents in sub-Saharan Africa (SSA). Research has shown that mortality among adolescents increases with transfer from pediatric to adult care due to poor retention in care, low viral suppression and poor psychosocial wellbeing. Majority of these deaths occurred in SSA. Few countries in SSA have an evidence-based protocol to transition ALHIV from pediatric to adult care. Nigeria has an estimated 160, 000 to 200,000 adolescents living with HIV (ALHIV), making it the country with the 2nd highest burden of HIV. In 2013, Nigeria accounted for ~10% of the deaths, with an estimated 11,000 AIDS-related deaths among adolescents. While previous national policy documents in Nigeria have recognized HIV among adolescents as an issue, none of these documents provide a comprehensive policy on ALHIV and none has any focus on transition of care. Nigeria is one of 25 target countries identified by the UNAIDS, UNICEF and partners in the ?All in to End Adolescent AIDS? initiative. ?All In? focuses on adolescents as part of the fast- track goals to end the HIV epidemic by 2030. The proposed research is designed to identify feasible, acceptable and sustainable approaches to transition ALHIV from pediatric to adult care. It is timely, as the Federal Ministry of Health and partners are working on finalizing a strategy for adolescents and young people living with HIV in Nigeria. Our proposed cluster randomized trial will test the comparative effectiveness of an Adolescent Coordinated Transition (ACT) program (Intervention Group; IG) versus the standard of care that abruptly transfers adolescents to adult care (Control Group, CG), on retention in care, viral suppression and psychosocial wellbeing among 216 HIV-infected Nigerian adolescents. Twelve healthcare facilities from all six geo-political zones will be randomly assigned (1:1) to IG or CG. ACT is a combination of a graduated transition program plus a pre-and post-transition peer-led Organized Support Group. The primary outcome is post-transition retention in care among ALHIV. Secondary outcomes are the difference among the groups in viral suppression rates and psychosocial wellbeing measured by improvement in perceived mental health status and the shift from external to internal health locus of control. This proposal is a collaboration among five members of the Nigeria Implementation Science Alliance (NISA) that currently serve nearly 25,000 ALHIV across all 36 states in Nigeria. NISA members have expertise in the implementation of nationally-supported programs for people living with HIV in Nigeria. Collaborators includes: Institute of Human Virology Nigeria; Family Health International 360, AIDS Prevention Initiative in Nigeria, Center for Clinical Care and Clinical Research Nigeria, and Center for Integrated Health Programmes (local program implementation and coordination); Nevada State College (statistical analyses and mediation/moderation analysis), and University of Nevada, Las Vegas (overall oversight of program implementation and evaluation).